Method of forming multiple layer structures including magnetic domains

ABSTRACT

A composite consisting of multiple layer structures, the basic structure of which is a chemically vapor deposited film on a substrate wafer, disclosed herein. The film is of such material appropriate for creating therein single wall magnetic domains which are capable of being moved about in predetermined directions within the thickness of the film and in the plane of the film. Devices are adapted to the film for sensing the motion of these domains thereby enabling application of these structures toward circuits which may be particularly utilized in memory or logic applications. A complete family of film on substrate materials are fabricated through a unique process, one of the steps of the process relates to establishment of the exact location of the substrate within the reactor at which deposition of the film upon the substrate is to be made in order to obtain the desired film characteristics. Included, are provisions for making multiple film layers to result in a matrix of films and hence a multitude of such circuits.

United States Patent Mee et al. 51 Feb. 29, 1972v [54] METHOD OF FORMINGMULTIPLE 3,511,702 5/1970 Jackson et a1. ..117 212 LAYER STRUCTURES{NCLUDING 2,919,432 12/1959 Broadbent ..340/174 MAGNETIC DOMAINS Jack E.Mce; David M. Heinz; Thomas N. Hamilton; Paul J. Besser; George R.Pulliam, all of Orange County, Calif.

Assignee: North American Rockwell Corporation Filed: Jan. 6, 1970 Appl.No.: 989

lnventors:

References Cited UNITED STATES PATENTS Bobeck et a1 ..340/174 M Pullian..1 17/235 Primary Examiner-William D. Martin Assistant ExaminerBernardD. Pianalto Attorney-L. Lee Humphries, H. Fredrick l-lamann, EdwardDugas and Martin E. Gerry [57] ABSTRACT A composite consisting ofmultiple layer structures, the basic structure of which is a chemicallyvapor deposited film on a substrate wafer, disclosed herein. The film isof such material appropriate for creating therein single wall magneticdomains which are capable of being moved about in predetermineddirections within the thickness of the film and in the plane of thefilm. Devices are adapted to the film for sensing the motion of thesedomains thereby enabling application of these structures toward circuitswhich may be particularly utilized in memory or logic applications. Acomplete family of film on substrate materials are fabricated through aunique process, one of the steps of the process relates to establishmentof the exact location of the substrate within the reactor at whichdeposition of the film upon the substrate is to be made in order toobtain the desired film characteristics. Included, are provisions formaking multiple film layers to result in a matrix of films and hence amultitude of such circuits.

6 Claims, 4 Drawing Figures PATENTEBFEBZQ 1912 SHEET 1 UF 3 i +3: mm B mw m S m A m H mm m v M U m W V -n 2. N 2 y III M Q a W W A m U/////////////A BY THOMAS N. HAMALTON PAIENTEGFEB 2 9 1972 INVENTORS BYSS R65 R, PULUAM AGENT p METHOD OF FORMING MULTIPLE LAYER STRUCTURESINCLUDING MAGNETIC DOMAINS BACKGROUND OF THE INVENTION 1. Field ofInvention The invention relates to a chemical vapor deposition processand product resulting therefrom for epitaxially growing oxygen compoundfilms of yttrium, lanthanum or any of the lanthanide group of elementsmixed with certain metals or other elements and deposited on a substratewafer comprising a variety of compounds for obtaining a composite of amultiple layer structure. This composite structure has utility inmagnetic devices as well as is particularly useful in logic devices orcircuits due to the capability of creation of single wall magneticdomains in the films thereof.

2. Prior Art The current interest in orthoferrite single crystals hasbeen aroused by the ability to produce mobile single domain wall orbubble magnetic domains in thin plates of proper crystallographicorientation as described in a paper by A. H. Bobeck entitled Propertiesand Device Applications of Magnetic Domains in Orthoferrites, publishedin the Bell System Technical Journal, Volume46, page 1901 (1967). Thesedomains can be manipulated by magnetic fields to perform logic andmemory functions as demonstrated in a patent to A. H. Bobeck et al. U.S.Pat. No. 3,460,l 16, issued Aug. 5, 1969.

Bulk orthoferrite crystals have been grown from solution,

either by a molten flux technique as described in a patent to J.

P. Remeika, U.S. Pat. No. 3,079,240, issued Feb. 26, 1963, or ahydrothermal technique as described in a paper by E. D. Kolb, D. L.Wood, and R. A. Laudise entitled The Hydrothermal Growth of Rare EarthOrthoferrite, published in the Journal of Applied Physics, Volume 39,page 1362 1968). Both growth methods as stated by the authors of thesepublications are prone to produce crystals with solvent inclusions orvoids, and solvent chemical substitution in the crystal is described forexample in a paper by J. P. Remeika and T. Y. Kometoni entitled LeadSubstitution in Flux Grown Single Crystal Rare Earth Orthoferrites,published in Material Research Bulletin," Volume 3, page 895 (1968) andthe above listed paper on hydrothermal growth by E. D. Kolb, D. L. Woodand R. A. Laudise. Single crystals resulting from either of these growthprocesses must be sliced and polished down to thin wafers of propercrystallographic orientation. Although very thin orthoferrite layers aredesired, the limit of mechanical polishing is a few thousandths of aninch beyond which breakage becomes excessive. In addition, polishingscratches must be eliminated for they impede magnetic domain motion.

Techniques are known for obtaining magnetic oxide films on crystallinesubstrates include spraying a suspension of reactants on heatedsubstrates, vacuum depositing metal alloys with subsequent oxidation,and chemically depositing on a substrate from mixed nitrate solutionsfollowed by a firing of the material. More recently, certain films havebeen prepared by electron beam evaporation and by RF sputtering.

Cech and Alessandrini in a paper entitled Preparation of FeO, MO, and CCrystals by Halide Decomposition," published in Transaction of theAmerican Society of Metals, Volume 50, page 150 (1959), reported theepitaxial growth of certain materials by a chemical vapor depositionmethod. Others independently extended the techniques reported and showedthat complex metal oxides could also be grown epitaxially by thechemical vapor deposition method. In general, chemical vapor depositionmethods have produced films with desirable properties but the films havebeen difficult to reproduce.

As has been reported by A. H. Bobeck, R. F. Fischer, A. J. Pemeski, J.P. Remeika and L. G. Van Uitert in a paper Application of Orthoferritesto Domain Wall Devices, published in the IEEE Transactions on Magnetics,Volume MAG-5 (1969), there is a minimum domain diameter for eachorthoferrite which is characteristic of that material at roomtemperature and for. which a specific sample thickness is required. Oneway of reducing the characteristic domain diameter that has beendescribed in the literature by V. F. Gianola, D. H. Smith, A. A. Thieleand L. G. Van Uitert in a paper Material Requirements for CircularMagnetic Domain 7 Devices," published in the lEEE Transactions onMagnetics," Volume MAG-5 (l969), is for example to form solid solutionswith samarium orthoferrite which has properties that depress the minimumdomain diameter.

Sheets or films of polycrystalline magnetizable metals which may besubjected to magnetic influences for the purpose of creating magneticdomains have been shown in a patent to K. D. Broadbent, U.S. Pat. No.2,919,432, issued Dec. 29, 1959. That patent specifically describes athin sheet domain wall shift register in which a reverse magnetizeddomain, bounded by leading and trailing domain walls, is nucleated at aninput position in the sheet and propaged along a first axis in the sheetby a step-along multiphase propagation field. Such a domain wall deviceusually requires or is characterized by anisotropic magnetic sheet wherepropagation of a reverse domain is either along the easy or the hardaxis and the domain walls bounding that reverse domain extend to theedge of the sheet in the direction orthogonal to the axis ofpropagation. inasmuch as the walls of the domain are bounded by the edgeof the sheet, propagation of those domains is constrained to one of theaxis along a transverse direction of the sheet.

In a patent to A. H. Bobeck et al. U.S. Pat. No. 3,460,l 16, issued Aug.5, 1969, it is shown that a reverse magnetized domain may be bounded bya single wall domain. Such a domain differs from the reverse domainpropagated in the Broadbent patent in that the single wall domain,encompassing the former, has a cross-sectional shape independent of thebreadth of the sheet, or in other words is not bounded by the edge ofthe sheet. These domains are referred to as single wall domains. v

The major disadvantages of both the Broadbent and Bobeck patents arethat the former resorts to the use of an anisotropic film or sheet ofmaterial which results in striped or fingerlike domains substantiallyacross the entire width or length of the sheet, while the latter patentdoes not utilize a substrate wafer for providing structural support ofthe sheet of material, thereby preventing the formation of very thinsheets of material for example thicknesses below 25 microns which offeradvantages in high domain density applications.

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide a chemical vapor deposition process for'epitaxially producing atleast one film, containing oxide compounds having apseudoperovskite-type structure comprised of at least one elementselected from the group consisting of the lanthanides, lanthanum oryttrium and having at least another element selected from the groupconsisting of aluminum, gallium, indium, scandium, titanium, vanadium,chromium, manganese and iron. The pseudoperovskite for perovskiteliketype of crystal structure is one having atoms with thesymmetricalrelationship of those in a perovskite lattice, but which hasbeen distored from cubic symmetry. This film is deposited by the processstated below on an oxide substrate compound wafer having at least oneelement selected from the group consisting of the lanthanides,lanthanum, yttrium, magnesium, calcium, strontium, barium, lead,cadmium, lithium, sodium or potassium, and having at least anotherelement which is selected from the group consisting of gallium, indium,scandium, titanium, vanadium, chromium, manganese, iron, rhodium,zirconium, hafnium, molybdenum, tungsten, niobiu, tantalum or aluminum.

It is a further object of the invention to provide the stated film onthe substrate so as to enable extremely thin films to be chemicallydeposited and structurally supported thereon.

1 It is still a further object to provide a film compound attached tothe substrate wafer wherein the film may be suitable for producingsingle wall magnetic domains therein, the single wall-magnetic domainsbehaving ina manner attributable to a single wall domain within avirtually isotropic medium. The

behavior of the single wall magnetic domain and an exemplary deviceshowing utility of said domain is described in detail in the inventionto A. H. Bobeck et al., US. Pat. No. 3,460,l l6, issued Aug. 5, 1969,and for the purpose of describing the theory of operation of the deviceset forth therein, and the principles of creating, propagating andsensing single wall magnetic domains in virtually isotropic films, thispatent is incorporated herein by reference.

It is therefore also an object of this invention to provide a processand a film-on-substrate structure wherein the film and substrateprovided will be single crystalline in character and where said at leastone film will have virtually isotropic magnetic characteristics in theplane of the film, and alternatively have embedded or attached theretomeans for providing at least one single wall domain in the film atpredetermined locations in the film, means for propagating said singlewall domains in any direction parallel to and within the plane orthickness of the film, and sensing means which are responsive topropagation of the single wall domain so as to determine the shift orpresence of the single wall domain within said film.

It is yet a further object to utilize the properties of the film oncedeposited on the substrate and the single wall magnetic domains thereinas may be created, for a multitude of purposes, one of which isaddressed to logic circuitry -applica tions.

It is a further objective to provide a plurality of such films ashereinabove statedinclusive of the several means for creating,propagating and sensing single wall domains therein on the samesubstrate for providing integrated logic devices.

Briefly in accordance with the invention, a plurality of films andsubstrates as hereinabove stated have been determined usable for thepurpose of creating magnetic domains in predetermined locations,propagation thereof in substantially all directions in the plane of saidat least one film with virtually equal degree of energy applied to movesaid domain and with means for sensing the shift in position of any ofsaid magnetic domains for logic circuit applications. The structure of ashift register, illustrated and completely described in the Bobeckpatent, are therefore described hereinbelow with respect to suchcomponent portions as are adapted to or are in magnetic communicationwith the film itself for execution of the creation, propagation andsensing functions of the magnetic domains. The equipment external to thefilm per se is not illustrated, as exemplary equipment used inconnection with devices having single wall magnetic domains andpropagation thereof are completely explained in the Bobeck patent. Theinstant invention, however, utilizes specific compounds for both thefilm and the substrate wafer which provide the desired results withadded advantages of providing structural support for the film so thatvery thin film of less than 25 microns thick, formed by the inventiveprocess to provide advantages of very small domain areas and hencehigher densities of single wall magnetic domains.

In films of single crystalline rare earth orthoferrites, it is possibleto establish cylindrical magnetic domains. The net magnetizationdirection of these domains in most orthoferrites is perpendicular to the(001 plane at room temperature. With application of an increasingmagnetic field to oppose the domain magnetization, the cylindricaldomains shrink to a minimum diameter and then collapse. For manyapplications, high densities of domains, and hence small domaindiameters, are desirable.

One way of reducing the domain diameter results from the type of growthdescribed herein which makes use of the magnetostrictive effect inepitaxial deposits. On cooling from the deposition temperature, thedifference in thermal expansion between the deposit and the substrateproduces mechanical strain in each. The deposit can be properly strainedso that the magnetostrictive effect reduces the effective anisotropyconstant in epitaxial (OOI) orthoferrite films. Since the domaindiameter is proportional to the anisotrophy constant, the

minimum domain diameter is reduced. Even if the magnetostrictive effectis not completely isotropic, it would not appreciably affect thevirtually isotropic motion of cylindrical domains in the (001 plane.

Chemical vapor deposition of orthoferrite films on oriented substratesprovide quite pure orthoferrites since extraneous chemicals which mightbe incorporated into the crystal are not present. Epitaxial films canroutinely be controlled to a fraction of a thousandth of an inch bycontrolling the duration of the growth process. Since substrates areoriented and polished before being used, no polishing of theorthoferrite is necessary. Thus chemical vapor deposition oforthoferrite films yields deposits which are purer, more perfect andthinner than bulk crystal growth methods.

The inventive process includes such steps as are necessary to determinethe best physical location of the substrate in the reaction chamber inorder to obtain the desired deposit of film on the substrate. Theprocess also includes the steps of elevating the temperature of asubstrate (or seed) crystal in a reaction chamber and reacting oxidizinggases and/or oxygen with gases of certain metal halides at the substratecrystal or wafer surface to deposit film as well as depositing amultiple number of films insulated from each other.

The process further provides for depositing films of single crystallinestructure on single crystal substrate wafers in accordance with thematerials selected, and in accordance with the control steps usedtowards accomplishment of the aforesaid product or group of products.

The process described herein contains a sequence of steps necessary todetermine the proper deposition conditions and the best physicallocation of the substrate in the reaction chamber in order to reproducethe desired type of deposit.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross section view of thereaction chamber used in the inventive process;

FIG. 2 is a plan view of a shift register illustrative of one type ofdevice that may be fabricated by the inventive process;

FIG. 3 is a cross section taken at plane 33 of FIG. 2 showing details ofthe wires embedded in a layer. These wires are used for connecting toexternal equipments for generating, propagating and sensing motion ofthe single wall magnetic domains created in the film of the device; and

FIG. 4 is a cross section taken at plane 3-3 of FIG. 2 showing amirror-image film and layer containing wires embedded therein on bothmajor deposition surfaces of the substrate.

EXEMPLARY EMBODIMENT In chemical vapor deposition processes, reactantvapors are brought together near a crystal substrate (or seed) so thatthey react to deposit an orthoferrite film on a substrate wafer.Chemical vapor depositions involve the reaction between a lanthanide,lanthanum or yttrium halide and an iron halide and oxygen, although notlimited to these elements or compounds. The reaction chamber permitsevaporation of the individual metal halides and intimate mixing of thevapors before they react with oxygen gas.

FIG. 1 illustrates a T-shaped reactor as shown at 10 for use in filmdeposition. FIGS. 2 and 3 are illustrative of a logic device created bythe process. The reactor is designed for relatively high temperatures toaccommodate for example the low volatility of metallic halide sourcematerials. The T-shaped reactor includes horizontal chamber 20 andvertical chamber 30. Disposed about the horizontal chamber is reactionzone heater 21. Individual heaters 31, 32, and 33 are disposed about thevertical chamber to control source material temperatures. Enclosedwithin the vertical chamber are crucibles 34 and 35 for retaining sourcematerials therein. These crucibles are inserted in premix tube 36,positioned and adjusted to their proper locations, are held thereat andare enclosed within premix tube 36. Tubular means 37 has an inlettherein for introducing I-ICl gas therein as an aid in transporting thesource material in crucible 34 so as to transport the source materialthereof in gas form to. reaction chamber 20. Tubular means 37 is alsoused for raising or lowering crucible 34 within premix tube 36. Crucible35 is adjusted within the premix tube by means of support rod 38.Tubular inlet 39 is provided in premix tube 36 for injectiontherethrough of helium vapors. The entire premix tube 36 containingcrucibles 34 and 35 together with ends of members 37, 38, and 39,extending from the premix tube can bemoved up or down vertically asdesired within chamber 30. Premix tube 36 is provided with an exitopening 40 at the upper end thereof for conducting the vaporized sourcematerials mixed with the several carrier gases injected into the premixtube 36. I

The flow rate of the source material from crucible 35 can be varied byvarying the temperature of heater 33 for the particular embodimentshown. The flow rate of the source material from crucible 34 can also bevaried by varying the temperature of heater 31 and, in addition, byvarying the flow rate of the gas introduced into the crucible from theinlet of means 37. The horizontal reaction chamber includes inlet 22through which helium and oxygen gases may be injected, and has exhaustoutput 23 for emitting gases from the chamber. The gases from opening 40transport the premixed metal halide vapors into the reaction zone of thereactor.

The crystal (or seed) substrate 26 is placed on a fused-silica holder 25in horizontal chamber 20. The position of holder 25 may be adjustedduring the process if desired.

Generally, during the process, the temperature of the crystal substratewafer is elevated by means of the reaction zone heater 21,. The sourcematerial heaters 31, 32 and 33'are elevated to temperatures whichprovide approximately 0.1 atm. of vapor pressure of each metal halide.

After each heater has reached the desired temperature the premix tube 36containing the source material crucibles 34 and 35 is raised intoposition in the vertical chamber 30. Gases are introduced into thevertical chamber through inlet in member 37 and through tubular means 39to conduct the metal halide vapors through opening 40 of the premix tubeinto the horizontal reaction chamber 20. Oxygen from inlet 22 of chamberis then reacted with the metal halidevapors at the upper portion thecrystal surface to produce the desired growth compound thereon.Specifically, an example of a typical reaction is expressable in thefollowing approximate formulation: v

The substrate crystal for the gadolinium orthoferrite film may beyttrium orthoaluminate or one of the other substrate compounds listedhereinbelow. Anhydrous gadolinium chloride (GdCl and iron (11) chloride(FeCl are contained in individual crucibles in their separatetemperature zones of chamber 36.

Dry helium is introduced into the premix tube at inlet 39 to transportthe GdCl and FeCl vapors, which are the reacting vapors of the metalhalides, from the crucibles into the reaction zone of the horizontalchamber 24). Dry hydrogen chloride (HCl) gas introduced at inlet 37flows directly into crucible 34 which holds the GdCl The HCl gas sweepsthe heavy GdCI vapors out of the crucible into the helium gas stream andprevents the very reactive GdCl vapors from reacting at anuncontrollably fast rate with the oxygen gas from inlet 22. Helium isinjected through inlet 22, along with oxygen into the horizontal chamber20.

The reaction deposition zone is in the downstream portion of thehorizontal chamber in proximity of the T-junction of chambers 20 and 30.The substrate wafer 26 is placed on holder which is inserted into theupstream portion of chamber 20. The process parameters such as heat fromheaters 31, 32 and 33 and gas flows through 22, 37 and 39 members may beadjusted until the desired reaction conditions are obtained, at whichtime substrate seed or wafer 26 on quartz holder 25 may be positioned inthe downstream portion of chamber 20. To obtain information as to theexact location where the desired vapor is ready for deposition on thesubstrate, a test sample material similar to wafer 26 or a fused quartztest plate may be inserted on holder 25 in the proximity of theT-junction. A reddish-brown colored film will deposit on the materialsubstituting for wafer 26 indicative of the orthoferrite depositionzone, when conditions for deposition and location of deposition zone areboth proper. Only 2 to 4 minutes of reaction time is used for this test.Thereafter, the substituting test-sample is removed and substrate 26 onholder 25 is inserted into chamber 20 through inlet 22 and positionedexactly as determined by the calibrations on rod 28 which isdeterminative of test sample positioning, so that vapors of the reactionare permitted to be deposited on the upper surface of substrate 26,thereby forming the desired monocrystalline film on the monocrystallinesubstrate wafer.

Details as to the positioning of the substrate in chamber 20 areimportant. Holder 25 has apertures 27 at either end thereof which areused for inserting therein a hooked-end of calibrated rod 28. Rod 28positions holder 25 in its proper location so as to obtain thereddish-brown deposition on the test sample. When the reddish-browncolor is obtained, the marking at rod 28 coinciding with the edge ofopening 22 is noted, so that holder 25 with actual substrate 26 thereonmay be reinserted and exactly positioned at the location where thereddish-brown deposition occurred. Rod 28 is removed thereafter untilthe film has been completely deposited, at which time rod 28 is againused for removing holder 25 together with deposited film 29 on substrate26. i

It should be noted that normally the film will deposit on the surface ofthe substrate 26 which is not contiguous or in contact with holder 25.Upon deposition of the film on one surface thereof, the other surface,previously in contact with holder 25 may be coated with a similar filmby simply inverting the substrate so that the now-coated surface isadjoining the surface of holder 25.

It should also be noted that the above-stated process may be used inconjunction with a mask for masking such upper portions of the uppersurface of substrate wafer 26 that are not desired to be coated withfilm 29 and leave such portions as desired tobe coated uncovered by themask, a plurality of films such as 29 on any one surface of substratewafer 26 may therefore be produced in this manner.

Films are formed on substrates in accordance with the examples in theTable 1 below, which specifies the control process parameters that wereconsidered.

TABLE 1 crystallographic (OOUGdFeO,

(OOUYFeO (IOUYFeO orientations (OOl )YAlO (l0)CaTiO,( l0! )YAIO,

Although only details of several compositions have been illustrated inTable 1, it is understood that all compositions as composed of theelement formulations given in Table 2, below are applicable to thisinvention.

Several combinations of film and substrate materials have beenillustrated as examples in Table 1, above. However, a number of othercombinations may be provided by combining at least two of the elementsof the film material with at least two of the elements of the substratematerial indicated in Table 2, below. Wherein, the film material is tobe used for providing single wall magnetic domains, one of the two elements thereof should be the element iron (Fe).

TABLE 2 Film Compound Substrate Compound The elements of the group oflanthanides are herein defined as cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium.

Following deposition of a single crystalline orthoferrite layer on asubstrate, useful devices may be made from the orthoferrite, such asdescribed by US. Pat. No. 3,460,116. Referring to FIGS. 2 and 3, a shiftregister is shown at 100. A similar shift register is substantiallydepicted in U.S. Pat. No. 3,460,116 and its manner of operation isdiscussed in detail therein.

The device 100 shown in FIGS. 2 and 3 which will therefore be made bythis process will be comprised of substrate 26 with film 29 depositedthereon. When the device at 100 having the capability of producing,propagating and sensing single wall domains is completed, theconfiguration will include at least one insulating layer 101 such assilicon monoxide (Si()) or Magnesium fluoride (MgF which will beattached to film 29 and have the several means for producing,propagating and sensing single wall domains embedded therein and heldsecurely thereby.

One approach to preparing layer 101, includes evaporating a metallicconductor 102 on the surface of film 29 through a suitable masksuperimposed on the surface of film 29, said mask having the pattern ofconductor 102 therein. This evaporation may be performed in a chambersimilar to that shown in FIG. 1, wherein the contents of vessel 34 aremetallic granules such as copper, gold, silver or aluminum, the othervessel 35 being removed, temperatures adjusted and oxygen floweliminated. Following this step, the mask is removed and vessel 34 maybe loaded with the insulating granules such as MgF which are evaporatedand deposited as a film over conductor 102 and over the remainingunexposed surface of film 29. Thereafter, another mask having pattern ofwire 103 may be superimposed on the insulating surface and by havingsuitable metallic material in vessel 34, the pattern of wire 103 may bedeposited in a similar manner as the pattern of conductor 102 wasdeposited. After removing the mask of wire 103, an additional coating ofinsulating material may be deposited over the surface of wire 103 andover the remaining portions of the previously deposited insulating film.A mask having pattern of wire 104 may then be laid down over theinsulating surface and additional conductive material deposited by thesame evaporation method used to form wire 104. Similarly, wires 105 andl06-may be formed by having the patterns thereof in masks as wire 104and additional conductive material deposited. Also similarly, the masksbeing removed, additional insulating material is deposited over wires104, 105 and 106 and over the unexposed insulating surface upon whichsaid wires have been deposited. A mask having pattern of wire 107 isthen laid down over the surface and wire 107 is formed in a similarmanner to formation of the other wires on the insulating surface. Themask is then removed and additional insulating material is depositedover the wire 107 and the unexposed insulating surface in the samemanner as previously accomplished. A mask having a pattern of wire 108is then laid over the insulating surface and conductor 108 is formed bythe same vacuum deposition method. Finally, the mask is removed andinsulating material is deposited over conductor 108 covering saidconductor and possibly portions of the remaining unexposed insulatingsurface, thereby encapsulating all the wires within layer 101 which isnow firmly attached to the surface of film 29.

It is noted that in connection with the deposition of wires 104, 105 and106 and at their crossover points, and possible crossover with wires102, 103, 107 and 108, that a wire need not be deposited in its entiretyat one time, which results in the requirement that insulating materialbe deposited between these various wires at their crossover locations.Suitable masks may be used in providing portions of wire depositions andinsulation depositions so that the total number of individualdepositions may be reduced.

It is noted that by using a suitable mask in conjunction with theprocess of providing layer 101 to cover such portions as are not desiredto have a layer such as 101 formed thereon and by leaving uncovered bythe mask such portions as desired to be formed with layers such as layer101, a plurality of layers such as layer 101 on any one surface of film29 or on groups of films such as 29 may be produced in the same manneras layer 101 was produced.

FIG. 4 illustrates deposition ofa film 29' on the other major unexposedsurface of wafer 26 and thereon layer 101'. Film 29' is identical insubstantive matter as film 29, and layer 10!, is identical to layer 101.Both films 29 and 29 are therefore deposited in the same way, and bothlayers 101 and 101' are also both deposited in the same way and maycontain the identical wires embedded therein. FIG. 4, is thereforeillustrative of a multilayer device having magnetic domains. It is alsoconceivable that multiple films of magnetic nonmagnetic materials on topof each other may be deposited sequentially on the same side of thesubstrate surface, employing 10 combination for film formation fromTable 2 to produce the magnetic and/or nonmagnetic layers of filmsand/or substrates.

A useful orthoferrite device at 100 will require means 101 forgenerating, propagating and detecting single wall magnetic domains infilm 29, A current pulse in loop 103 provides means for drawing apositive region from border of device 100 up to location 110, and apulse on wire 104 at 111, isolates a portion of the positive region atlocation 110, thereby generating a single wall magnetic domain thereat.By sequentially pulsing wires 104, 105. and 106 respectively at 111,112, and 113, the single wall magnetic domain is propagated along theshift register shown herein from location 110 to intermediate locations125 and 126, ultimately terminating at location 114. At location 114, aninterrogation pulse in wire 107 collapses the single wall magneticdomain, inducing a detection pulse in wire 108.

The shift register device has been discussed for the purpose of enablingthe illustration of the types of additional fabrica tion processesrequired in connection with the orthoferrite layer on a substrate in theform of a useful device. Other types of devices may also require currentcarrying conductors, and in addition, employ magnetic layers,semiconductor layers or external optical light source and otherdetecting components. Wire 102 is connected to an initializing circuitfor providing a pulse therein so as to rearrange the domains in film 29to provide the border thereof as explained in US. Pat. No. 3,460,l 16.

in another approach to preparing layer 101, the current carryingconductors may be metal films laid down by vacuum evaporation.Typically, copper, aluminum, or gold may be used. The conductor patternsmay be defined by masking during evaporation, or the entire area may becoated and the patterns defined by photolithographic etching processes,well known in the semiconductor device arts. Each of the conductors mustbe electrically isolated from the others so that layers of insulation,such as silicon monoxide (SiO) or magnesium fluoride (MgF may beevaporated between metal evaporations as hereinabove described. Hereagain, the region covered by the insulating material may belimited bymasking during evaporation or the entire area may be coated and patternsdefined by photolithographic etching processes. The number of separateevaporation steps will depend on the number of conductor crossovers, andthe ingenuity in designing patterns for conductor and insulatordepositions.

For other types of devices which employ magnetic or semiconductor layerson the surface of the orthoferrite films, suitable layers may bedeposited by vacuum evaporation or chemical vapor deposition. Typically,magnetic nickel-iron alloy compositions may be evaporated on certainregions of the orthoferrite layer to provide small local fields whichassist in holding or moving the single wall magnetic domains.

It should be noted that the wires shown in layer 101 or 101' could havealso been replaced by magnetic means communicating with the film orfilms to create, propagate and/or sense the change in position of thecreated and propagated single wall magnetic domains.

It should be also noted that the additional film 29' deposited on thesubstrate as shown or in such other manner as described is also of thepseudopervoskite-type structure and single crystalline.

Hence, due to the magnetization requirements, the components of filmformulation would be iron and the remaining metallic component may beone or more of the elements detailed in Table 2. The magnetic materialsor compounds of films 29 or 29' will have a first magnetizationdirection substantially orthogonal to an imaginary plane parallel to thethickness of said film and providing for at least one single wallmagnetic domain with a second magnetization direction oppositeto thefirst magnetization direction and having a boundary unconstrained alongsaid second magnetization direction, said single wall magnetic domainbeing free to move in a plurality of directions substantially orthogonalto the second magnetization direction. At least one of the constituentsof the JO combination of the substrate wafer formulation is differentfrom at least one of the constituents of the JQ combination of the filmformulation. Such difference stresses the film which may therebycontribute to a substantial reduction in the area of the magnetic domainthus formed. The area of the domain, by the means established forcreating same, is oriented orthogonally to the second magnetizationdirection, such area lying in said imaginary plane.

We claim:

1. A method of forming a composite structure suitable for containingbubble domains therein comprising the steps of providing a singlecrystal substrate, and forming a magnetic single crystal film on saidsubstrate with sufficient mechanical strain in said film to provide saidfilm with sufficient uniaxial anisotropy for the formation of bubbledomains therein, said film having a thickness less than 25 microns andsufficient magnetization for the formation of bubble domains therein,whereby said film has a JQO formulation wherein, the J constituent ofsaid film formulation has one element selected from the group consistingof cerium, praseodymium, neodymium, promethium, samarium, europium,gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium,lutetium, lanthanum, and yttrium, and

the Q constituent of said film formulation is taken from the groupconsisting of iron, aluminum, gallium, indium, scandium, titanium,vanadium, chromium and manganese. 2. A method as described in claim 1where said 0 constituent of said film formulation is iron.

3. A method as described in claim 2 whereby said single crystalsubstrate has a JQ-oxide formulation wherein:

the J constituent of said substrate formulation is at least one elementselected from the group consisting of cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, lanthanum, yttrium,magnesium, calcium, strontium, barium, lead, cadmium, lithium, sodiumand potassium; and the Q constituent of said substrate formulation is atleast one element selected from the group consisting of indium, gallium,scandium, titanium, vanadium, chromium, manganese, rhodium, zirconium,hafnium, molybdenum, tungsten, niobium, tantalum, and aluminum. 4. Amethod as described in claim 2 whereby the film is formed by the stepsof,

conducting at least one of a plurality of metal halides into thereaction chamber, injecting at least one reacting gas and at least onecarrier gas into the reaction chamber reaction therein with the metalhalides thereby producing reaction products of the halides and gases,inserting a test sample for selecting the location of said substratewithin said reaction chamber, removing said test sample, and insertingsaid substrate at the selected location for deposi' tion of at least oneof the reaction products on said substrate to form said monocrystallinefilm thereon. 5. A method as described in claim 3 whereby: said Jconstituent of said substrate formulation is at least one elementselected from the group consisting of cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, lanthanum and yttrium;and said O constituent of said substrate formulation is at least oneelement selected from the group consisting of indium, gallium, scandium,titanium, vanadium, chromium, manganese, rhodium, and aluminum. 6. Amethod of forming a bubble domain comprising the steps of providing asingle crystal substrate, and forming a first magnetic single crystalfilm on said substrate with sufficient mechanical strain in said film toprovide said film with sufficient uniaxial anisotropy for the formationof bubble domains therein and having a thickness less 'than 25 microns,whereby said film has a JQO formulation wherein, the J constituent ofsaid film formulation has at least one element selected from the groupconsisting of cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbitaken from thesame groups as set forth for said first single crystal film, and saidsecond film having sufficient mechanical strain therein to providesufiicient uniaxial anisotropy for the formation of bubble domainstherein and having a thickness less than 25 microns.

2. A method as described in claim 1 where said Q constituent of saidfilm formulation is iron.
 3. A method as described in claim 2 wherebysaid single crystal substrate has a JQ-oxide formulation wherein: the Jconstituent of said substrate formulation is at least one elementselected from the group consisting of cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, lanthanum, yttrium,magnesium, calcium, strontium, barium, lead, cadmium, lithium, sodiumand potassium; and the Q constituent of said substrate formulation is atleast one element selected from the group consisting of indium, gallium,scandium, titanium, vanadium, chromium, manganese, rhodium, zirconium,hafnium, molybdenum, tungsten, niobium, tantalum, and aluminum.
 4. Amethod as described in claim 2 whereby the film is formed by the stepsof, conducting at least one of a plurality of metal halides into thereaction chamber, injecting at least one reacting gas and at least onecarrier gas into the reaction chamber reaction therein with the metalhalides thereby producing reaction products of the halides and gases,inserting a test sample for selecting the location of said substratewithin said reaction chamber, removing said test sample, and insertingsaid substrate at the selected location for deposition of at least oneof the reaction products on said substrate to form said monocrystallinefilm thereon.
 5. A method as described in claim 3 whereby: said Jconstituent of said substrate formulation is at least one elementselected from the group consisting of cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, lanthanum and yttrium;and said Q constituent of said substrate formulation is at least oneelement selected from the group consisting of indium, gallium, scandium,titanium, vanadium, chromium, manganese, rhodium, and aluminum.
 6. Amethod of forming a bubble domain comprising the steps of providing asingle crystal substrate, and forming a first magnetic single crystalfilm on said substrate with sufficient mechanical strain in said film toprovide said film with sufficient uniaxial anisotropy for the formationof bubble domains therein and having a thickness less than 25 microns,whereby said film has a JQO3 formulation wherein, the J constituent ofsaid film formulation has at least one element selected from the groupconsisting of cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, hoLmium, erbium, thulium,ytterbium, lutetium, lanthanum and yttrium, and the Q constituent ofsaid film formulation is taken from the group consisting of iron,gallium, indium, scandium, titanium, vanadium, chromium, and manganese,and forming a second magnetic single crystal film having a JQO3formulation wherein said J and said Q constituents are taken from thesame groups as set forth for said first single crystal film, and saidsecond film having sufficient mechanical strain therein to providesufficient uniaxial anisotropy for the formation of bubble domainstherein and having a thickness less than 25 microns.